Does Mn²⁺-Mn²⁺ Spin-Exchange Interaction Involve Mn²⁺ Luminescence of Mn²⁺-Doped/Concentrated Materials?

Mn²⁺-doped luminescent quantum dots play a vital role in the fields of optoelectronic materials and devices. The presence of five unpaired d electrons in Mn²⁺ ions facilitates spin-exchange interactions, profoundly influencing the spin state of the exciton and thereby impacting the optical behaviors. However, the involvement and specific effects of spin-exchange interactions on optical properties of Mn²⁺ in insulating bulk phosphors remain a subject of controversy, attributed to the scarcity of solid evidence and the interference of various factors. In this Perspective, we delve into the fundamentals and recent advancements concerning the Mn²⁺-Mn²⁺ spin-exchange interaction in Mn²⁺ luminescent materials. The discussion encompasses various aspects, such as types of magnetic coupling, the coupling mechanism in optical ground state and excited state, as well as effective measures for verification. This Perspective underscores the existing knowledge gaps in Mn²⁺-doped bulk phosphors, highlighting significant opportunities for further exploration and advancement in both fundamental and applied research within this domain.